Electrochemical process for cutting beryllium

ABSTRACT

AN ELECTROCHEMICAL METHOD FOR CUTTING BERYLLIUM BY APPLICATION OF PRESSURE JETS OF ELECTROLYTE.

United States Patent O "ice U.S. Cl. 204-143 4 Claims ABSTRACT OF THE DISCLOSURE An electrochemical method for cutting beryllium by application of pressure jets of electrolyte.

The invention described herein was made in the course of, or under, AEC Contract No. W-7405ENG48 with the United States Atomic Energy Commission.

FIELD OF THE INVENTION Beryllium is cut electrolytically to provide damagefree, square edges and smooth surfaces by use of pressure jets of electrolyte containing nitrate ion in aqueous solution.

PRIOR ART Because of its low density and desirable properties, beryllium metal has found extensive uses in recent years. Its use, however, has been restricted by the difliculty of cutting beryllium bodies in general and thin sheets in particular. Beryllium is so brittle that previously used methods of separation tend to result in edges which are weakened by cracks and tears. The present invention solves these problems.

SUMMARY OF THE INVENTION According to the present invention, a jet of an aqueous electrolytic solution is directed at the beryllium work piece from an inert metal nozzle. The solution, as will be discussed below in greater detail, must have a certain composition. The nozzle, which is preferably made of platinum, serves as the cathode, and the beryllium work piece as the anode.

During the cutting of the beryllium, the nozzle is moved with respect to the beryllium work piece so that the point of impact of the electrolyte jet, accompanied by the flow of current, moves along the locus of desired separation.

For desirable results, several parameters should be controlled. The nozzle should be quite close to the beryllium work piece, generally a distance of 0.040 inch or less. The current flow through the electrolyte should be at least 0.5 ampere to obtain reasonable cutting rates at a potential difference of from 60 to 120 volts between nozzle and beryllium.

Only certain electrolytes work in the process of the present invention. The presence of nitrate ion is essential. The preferred electrolytes are ammonium nitrate, sodium nitrate and potassium nitrate. Nitric acid is also useful, as are mixtures of nitric acid and phosphoric acid.

The concentrations of the solutions are chosen to maximize their conductivity. The preferred strengths of the various solutions are 75% nitric acid; a mixture of 50% nitric and 33% phosphoric acids; 500 g./l. sodium nitrate; 250 g./l. potassium nitrate; 500 g./l. ammonium nitrate. Because of lack of corrosion problems and high solubility, ammonium nitrate is most preferred.

The optimum values for these various parameters are to some extent mutually interdependent. In particular,

3,556,963 Patented Jan. 19, 1971 this is the case in regard to the rate at which the nozzle traverses the work piece being cut, and the velocity of the jet of electrolytic solution. The jet of electrolytic solution should be sufficient to cause an erosive action on the beryllium, and to act to carry away the debris. For example, driving pressures of about 6 to 10 pounds per square inch to force the electrolyte through a 20 mil nozzle are satisfactory. Generally, electrolyte velocities of at least 5 meters per second have been found to produce the desired amount of force and washing action to effect a smooth U-shaped cut. At these rates of electrolyte flow and pressure, the nozzle, for best results, is moved over the work piece at a rate of at least 2 feet per minute, for the cutting of a thin beryllium sheet.

For continuous cutting of beryllium bodies of greater thickness, the work piece may be set into reciprocating or rotating motion in relation to the electrolyte nozzle, depending upon the geometry of the work piece. In like manner, the process may be adopted for planing beryllium to obtain smooth surfaces. It is very advantageous to use a high velocity stream of air or nitrogen to blow away any excess of electrolyte from the beryllium surface. It is also sometimes advantageous to have the work piece of beryllium in such a position that the spent electrolyte will drain away, but even in such cases, the use of a gas stream is very helpful because it serves to confine the action of the electrolyte jet and prevent erosion in adjacent areas.

It will be appreciated that the rate of nozzle traverse, the velocity of the electrolyte jet, the distance between the nozzle and the beryllium, and the voltage are all parameters which should be optimized for each particular job. With the present disclosure as a guide, however, the selecting of the optimum conditions is a matter of routine testing,

PREFERRED EMBODIMENTS Sheet specimens of beryllium are cut electrolytically by oscillating the work at nearly uniform linear speed normal to a jet of electrolyte. Listed below are the parameters for making a 2-inch long cut in 0.05-inch thick, high-purity beryllium sheet:

Electrolyte: Ammonium nitrate, 500 g./l. Temperature: 42 C.

Nozzle: Platinum tubing of 0.042-inch inside diameter Nozzle pressure: 5.7 p.s.i.g.

Operating voltage: 65 V. (DC. current 1.7 amps.) Electrode separation: 0.030 inch Work speed: 5 cycles/min.

A cut through 0.050 inch takes 35 minutes. Seven and one-half minutes are required to clean up the ridge on the back edge.

Accurate, rigid positioning of electrode, jets and work piece are maintained for satisfactory dimensional regularity and surface finish of cut edge.

The foregoing embodiment is given solely for purposes of illustration. Many variations will occur to those skilled in the art without departing from the spirit or scope of the present invention.

What is claimed is:

1. A process for cutting a beryllium body, comprising directing a thin stream of an aqueous solution containing nitrate ions from an inert metallic nozzle having an inside diameter of about .20 to 42 mils at the beryllium body from a distance of less than 0.040 inch, establishing a potential difference of from 60 to volts between said beryllium body, as the anode, and said body, as the cathode, causing a current of at least 0.5 amp, to flow through said stream of aqueous solution, and traversing the beryl- 0 Hum body with the stream of the aqueous solution. References Cited of t'rfieis Z1 15: si i fi oi aifiis ziiuzlif'iclfiifi UNITED STATES PATENTS beryllium body is at least 2 feet per minute. 2985050 5/1961 schwacha 83'177 3. A process as claimed in claim 1, in which the inert r 2,881,503 4/1959 Johnson metallic nozzle is Platinum 0 Balley 4. A process as claimed in claim 1, in which the aquev ous solution is of ammonium nitrate at a concentration JOHN MACK Primary Examiner of about 500 grams per liter. S. S. KANTER, Assistant Examiner 

